Notes

The field notes for the 1829 plan are at the Baker Library, Harvard Business School, Baldwin Family Business Papers,
Series I, subseries A, MC papers,1787-1855
iii. Surveys and drawings, 1794-1834.

Baldwin 1830 – 3.84' = NGVD29. For the derivation of the conversion factor between Baldwin's datum and NGVD29, see "THE 1825 IRON BOLT AND THE GREAT BILLERICA DAM CONTROVERSY"
http://middlesexcanal.org/towpath/TowpathTopics-Sept2013color.pdf. The top of the Middlesex Canal Dam's flashboards is el. 113.48' (Baldwin 1830).

miles, chains.links. One chain is 66 feet, 80 chains/mile, 100 links/chain.
|
27, 16.16 Merrimack River, 27-1/5 miles to lowest gate at Merrimack from lowest gate at Charles River.
Merrimack water of river, 89.45' - 83.25 = 6.2' - (3.5', design depth of canal) = 2.7', difference due to Pawtucket Dam in 1830? No dam mentioned in 1822 survey.
" highest gate sill, 107.56'
" lowest gate sill, 83.25 Sep 5, 1822 survey, 3.5' water over sill, av of two measurements.
lift 24.31' 113.48', iron bolt, - (83.25 + 3.5' design) = 26.73'
113.48', iron bolt, - 89.45, water of Merrimack River in 1830 = 24.03'. " - 24.03' = 2.7', difference due to first Pawtucket Dam in 1825 (1st dam, Malone, /Waterpower in Lowell/, p. 45). See boat entering stone lock, Allan Evans Herrick (1854-1931) in Clarke, p. 65., which show the wing walls, indicating the first Pawtucket Dam did not raise the water level to the point the lowest of the three locks was not needed. The 1825 temporary dam was replaced in 1830. Painting shows construction. Three years later, the dam had two feet added to elevation 32 feet, Locks & Canals datum. See Malone, p. 48.

22, 13.45 Timber Lock, "108.89 to sills" "Single Gates."

22, 3.26, "108.48' to lower gate Sill." [eastern gate of guard lock on west side] 108.48
- 83.25
25.23
22, 00.00 summit pond
113.70', water of river, above dam - 89.45, water of Merrimack River = 24.25' [Pawtucket Dam?]
102.97', " " " below Mills 1825 iron bolt, el. 113.48 (Baldwin1830) -0.73=112.75
10.73', difference in water level, above – below dam - 9" flashboards = 10.0'

21, 73.24, 109.25' [bottom of canal, at river, east side]

21, 62.62 "109.25' to lower Gate Sill." [western gate of guard lock on east side] 109.25
+ 3.50 - 83.25
112.75 26.00
Cf. Summit Pond above. The 0.73' for 9" flashboards is the dimension shown on the sections which were part of the 1861 engineers' report.

17, 75.55 Shawsheen Aqueduct
Sill, Nichol's Lock +3.5' = 112.20', water in canal, - 85.19, water in river, = 27.01' difference
Concord River at 113.70'

17, 32.48 Nichols' Lock, 108.70', upper gate sill – 101.07, lower gate sill = 7.63' lift.
upstream downstream
Sill elevations are used to draw the bottom of the canal.
Nichol's Lock, upper gate sill, el. 108.70 + 3.5' of water = 112.20

15, 61.88 Gillis or Jaques Lock, 101.04' to upper gate sill
94.12 to lower gate sill
6.92' lift

9, 37.98 Horn Pond, highest gate sill, 93.83', 49.83' higher than lowest gate sill.
9, 17.76 Lowest gate sill, el. 44.00'. The distance, 17.76, is calculated from the chain.link data in the 1829 plan field book. Six locks with an av lift of 8.3', length between sills of 84'.
Four boats in October, 1804. "The length of these is 74 feet, which I think (with their square corners) is just right, the breadth at the top as follows, two of them is 9'10" one 9'9" and one 9'8", the height of the sides of two of them is about 3'6" and one 3'4" and the other 3'3". I am satisfied as to the height of the sides, but they appear a little too upright, that is to say the boats are a little too broad at bottom say 9'8", 9'7" or thereabouts." Loammi Baldwin, TT, Sep 1972.

8, 41.07 Stone Lock and culvert for Horn Pond Brook, upper gate sill, 41.90', lift 6.98' (6.51' over highest Gardner sill). Lower gate sill, 34.92'. Cf. 35.39', highest gate sill, Gardner's Locks. Upper gate to lower wing wall, 98.3'. Located at north end of Middlesex St, Winchester 01890, north of intersection with Canal St, based on Waterfield, Winchester 1.


7, 0.76 Gardner's Locks, highest gate sill, 35.39', lift of two locks, 12.51', length 169.0'
[6, 78.20] lowest gate sill, 22.88'

0, 42.82 Malden Road Lock, lower gate sill, 4.44'. Upper gate sill 13.55'. Lift is not the difference between lower and upper, 9.11', because the upper gate sill, el. 5.29', at the Mill Pond Lock is higher. Lift at Malden, 13.55' – 5.29' = 8.26'.
Distance measured to upstream end of lock.

0, 30.93 Mill Pond Lock, upper gate sill 5.29' & the lower sill 3.91 above base line.
Lift, 1.38'.

0, 00.00 Tide Locks, 0.00', lower gate sill. "Upper gate sill 0.297 above base line."
Highest spring tides, 11.18', drawn even with height of upper tide lock.
High water, 8.07', July 16, 1830, drawn even with the height of lower tide lock.
Distance starts at river end of tide locks.
The Boston City Base is mean low tide. See footnote 54, p. 206, Boston's Back Bay by William Newman and Wilfrid E. Holton, 2006. BCB – 5.65 = NGVD29 = Baldwin 1830 – 3.84'. Then, BCB = Baldwin 1830 + 1.81'.